1. Field of the Invention
The present invention relates to a method for fabricating a semiconductor device, and more particularly to a method for fabricating a semiconductor device by using a PECYCLE-CVD (plasma enhanced cycle chemical vapor deposition) process.
2. Description of the Prior Art
Various semiconductor thin film deposition techniques including a CVD (chemical vapor deposition), a PECVD (plasma enhanced chemical vapor deposition), an ALD (atomic layer deposition), and a PEALD (plasma enhanced chemical vapor deposition) are well known in the art. However, they have disadvantages when depositing thin films for highly integrated semiconductor devices.
Hereinafter, various problems occurring in the conventional semiconductor thin film depositing techniques will be described with reference to FIGS. 1 to 12.
As shown in FIG. 1, according to a conventional CVD process, first source gas A and second source gas B are fed into a process chamber while the CVD process is being carried out in such a manner that a MO-source thin film 15 is deposited on a wafer through a chemical-vapor reaction between the first and second source gases A and B. In this case, not only is it difficult to control the gas and source, but also a lower layer is damaged due to a high process temperature, so that a process window is narrowed when depositing the semiconductor thin film. In addition, as shown in FIGS. 2, 3a and 3b, the step coverage and film uniformity become deteriorated, so that the conventional CVD process is not adaptable for achieving a micro-structure of a highly integrated memory device.
In addition, according to a conventional PECVD process as shown in FIG. 4, first and second source gases A and B and plasma are fed into a process chamber while the PECVD process is being carried out in such a manner that a thin film 25 is deposited on a wafer through a chemical-vapor reaction between source gases A and B and plasma. However, the PECVD process also makes it difficult to control the gas and source. Although the PECVD process is carried out at a temperature lower than a temperature of the CVD process, the step coverage and film uniformity still become deteriorated as shown in FIGS. 6a and 6b, so that the conventional PECVD process is not adaptable for achieving a micro-structure of a highly integrated memory device.
FIG. 7 shows a conventional ALD process. According to the conventional ALD process, a first purge process is carried out after first source gas A has been fed into a process chamber. Then, second source gas is fed into the process chamber and a second purge process is carried out, thereby forming a thin film, such as a Mo source thin film 35. As shown in FIGS. 8 and 9, the ALD process can easily control gas and source and achieve superior step coverage and film uniformity. However, since the ALD process has a low deposition speed, it is adaptable only for depositing a thin film. In addition, the ALD process has a disadvantage when fabricating semiconductor devices in mass-production.
FIG. 10 shows a conventional PEALD process. According to the conventional PEALD process, a first purge process is carried out after first source A has been fed into a process chamber. Then, second source gas B is fed into the process while generating plasma in the process chamber. After that, a second purge process is carried out, thereby forming a thin film, such as a Mo source thin film 45. As shown in FIGS. 11 and 12, the PEALD process can easily control gas and source and achieve superior step coverage and film uniformity. However, since the PEALD process also has a low deposition speed, it is just adaptable for depositing a thin film. In addition, although the PEALD process may solve problems of the ALD process, the PEALD process also has a disadvantage when fabricating semiconductor devices in mass-production.